1. Field of the Invention
The present invention relates to a telescopic support arm used in windows, inspection ports, doors of various devices and others.
2. Prior Art
Various telescopic support arms have been hitherto invented. For example, a support arm is designed in a telescopic structure by moving a piston rod reciprocally within a cylinder. Such a telescopic support arm is used by attaching its one end to a door and the other end to a door support frame.
In such a conventional telescopic support arm, however, when a door is opened forcefully until the telescopic support arm is fully expanded, impact then acts directly on the junction of the cylinder and the piston rod, and therefore the durability of the arm can not be sufficient, but rather poor. Or when such telescopic support arms are used at both sides of a door, if the door is attached to the support frame in a distorted state or if a gap is formed in mounting of the door on the support frame, either one or both of the telescopic support arms may not be fully expanded, and the door cannot be opened or closed smoothly.
Still more, in such a conventional telescopic support arm, the door cannot be stopped and hold at an arbitrary position, but is stopped only at the fully opened position or at a position of a preset opening width of the door. Therefore, if it is desired to stop the door at a slightly opened position or to vary the opening width of the door frequently, this type of telescopic support arm can not suffice these requirements.